Why people do the things they do is an age-old question. However, psychology—the science concerned with behavior, both human and nonhuman animals—is only about 125 years old. Despite its youth, it is a broad discipline, essentially spanning subject matter from biology to sociology. Biology studies the structures and functions of living organisms. Sociology examines how groups function in society. Psychologists study the intersection of two critical relationships: one between brain function and behavior, and one between the environment and behavior. As scientists, psychologists follow scientific methods, using careful observation, experimentation, and analysis. But psychologists also need to be creative in the way they apply scientific findings. Psychologists are frequently innovators, evolving new approaches from established knowledge to meet changing needs of people and societies. They develop theories and test them through their research. As this research yields new information, these findings become part of the body of knowledge that practitioners call on in their work with clients and patients. Psychology is a tremendously varied field. Psychologists conduct both basic and applied research, serve as consultants to communities and organizations, diagnose and treat people, and teach future psychologists and other types of students. They test intelligence and personality. Many psychologists work as health care providers. They assess behavioral and mental function and well-being, stepping in to help where appropriate. They study how human beings relate to each other and also to machines, and they work to improve these relationships. And with America undergoing large changes in its population makeup, psychologists bring important knowledge and skills to understanding diverse cultures. Many psychologists work independently. They also team up with other professionals—for example, other scientists, physicians, lawyers, school personnel, computer experts, engineers, policymakers, and managers—to contribute to every area of society. Thus we find them in laboratories, hospitals, courtrooms, schools and universities, community health centers, prisons, and corporate offices. Psychologists traditionally study both normal and abnormal functioning, and also treat patients with mental and emotional problems. They also concentrate on behaviors that affect the mental and emotional health and mental functioning of healthy human beings. For example, they work with business executives, performers, and athletes to reduce stress and improve performance. They advise lawyers on jury selection and collaborate with educators on school reform. Immediately following a disaster, such as a plane crash or bombing, psychologists help victims and bystanders recover from the trauma, or shock, of the event. They team with law enforcement and public health officials to analyze the causes of such events and prevent their occurrence. Involved in all aspects of our fast-paced world, psychologists must keep up with what's happening all around us. When you're a psychologist, your education never ends. According to economists at the Department of Labor, opportunities for people with graduate degrees in psychology are expected to grow between 10% and 20% by 2010. Opportunities for work in psychology are expanding in number and scope, especially for those with graduate degrees, while an undergraduate degree remains excellent preparation for continued graduate work in psychology or for another field, such as business, medicine, or computer science. The move toward preventing illness, rather than merely diagnosing and treating it, requires people to learn how to make healthy behavior a routine part of living. Indeed, many of the problems facing society today are problems of behavior, for example, drug addiction, poor personal relationships, violence at home and in the street, and the harm we do to our environment. Psychologists contribute solutions to problems through careful collection of data, analysis of data, and development of intervention strategies—in other words, by applying scientific principles, the hallmark of psychology. In addition, an aging America is leading to more research and practice in adapting our homes and workplaces for older people. The promises of the electronic revolution demand more user-friendly technologies and training. More two-career families in the workplace calls for employers to accommodate the needs of families. Psychologists are helping employers to make the changes that are needed. The diversity of America today calls for psychologists to develop and refine therapies to meet the unique needs of different ethnic groups. Furthermore, research advances in learning and memory, and the integration of physical and mental health care, make psychology more exciting than ever. Most psychologists say they love their work. They cite the variety of daily tasks and the flexibility of their schedules. They are thrilled by the exciting changes taking place in the field, from adapting technology to humans to working as part of primary health care teams. They are working hard to provide answers to research questions in diverse areas such as prevention, perception, and learning. Educators strive to train the next generations using new technology and knowledge. The study of psychology is good preparation for many other professions. Many employers are interested in the skills that psychology majors bring to collecting, analyzing, and interpreting data, and their experience with statistics and experimental design.